The roles of habitat and interspecific interactions in the ecology of amphibians

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One of the chief causes of declines in populations of wild species is habitat loss and degradation, disappearing amphibians are no exception. In Canada, an ongoing lack of information on the basic biology and habitat requirements of even common amphibians makes conservation a challenge. Over the next 5 years, my students and I will conduct three projects in Alberta that investigate how the wood frog, the most widespread amphibian species in Canada, uses wetland and upland habitat and how habitat use is shaped by interactions with humans, beavers, and fishes. Project 1 focuses on constructed and natural wetlands in Edmonton to determine what structural and functional features are required to maintain viable frog populations in urban environments. We will mark and track individuals to test the prediction that wood frogs use two strategies to survive in the city; some frogs are residents that remain permanently in narrow riparian strips around breeding ponds, whereas others migrate annually between urban ponds and natural woodland. Project 2 will determine if beavers, acting as ecosystem engineers, create and maintain wetland habitat for amphibians in the drought-prone Aspen Parkland. We will compare wood frog populations between sites with and without active beaver colonies and document how adults and tadpoles use ponds and riparian habitats affected by beaver construction and flooding. In many systems, fish, especially introduced species, can drastically reduce amphibian numbers. However, in small lakes in Alberta's boreal foothills, we found that stocked trout do not alter the size or structure of wood frog populations. To find out why, Project 3 will use experimental enclosures to examine interactions between rainbow trout, native minnows, and tadpoles from stocked lakes, lakes with only minnows, and fishless lakes. We predict that wood frogs from lakes with minnows have adapted to the presence of fish, and thus can persist when trout are introduced. As a whole my program will help us understand how amphibians use wetland and upland habitats to survive in the face of urbanization, climate change, and natural resource management.